642 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Pockets of Calcium Oxalate.* * * § — Dr. J. Wittlin lias investigated 
the mode of formation of the pockets of calcium oxalate (Rosanoff’s 
clusters) in a number of different plants and in different organs. As 
a rule, the crystals found in the cell-cavity are formed in the primordial 
utricle; each crystal becomes invested with a separate envelope of a 
similar nature to the cell-wall ; and this is true whatever the size of the 
crystals, even when they assume the form of raphides. In Citrus only 
were crystals found imbedded in the cell-wall. When the crystals are 
suspended from beams in the cell, the beams are derived from the 
envelopes of the crystals, and it is only at a later period that they coalesce 
with the cell-wall. The separate crystals occur in an especially charac- 
teristic form in the root-tubercles of Bobinia Pseudacacia, and in species 
of Qlycyrrhiza. Raphides never occur in pockets, and the structure of 
their envelope is of a different character, presenting the greatest resem- 
blance to fungus-cellulose. The crystals of calcium oxalate found within 
aleurone-grains have no visible envelope. 
(3) Structure of Tissues. 
Wood of Pomeae.'f — An examination of the structure of the wood in 
the various genera of Pomeae by Dr. A. Burgerstein shows a great 
uniformity in essential points. The most important differences are in 
the presence or absence of tertiary thickening layers in the vessels and 
tracheids ; in the radial width of the vessels ; in the height of the cells 
of the medullary rays ; and in the number of the rows of cells in the 
medullary rays. In the xylem of the root, the vessels are much larger 
than in that of the stem and branches ; the tracheids and wood paren- 
chyme-cells are broader, while the number of the medullary rays is 
smaller. Tertiary thickening layers are found in the xylem of the root 
as well as in that of the stem. 
Red Wood of Pines. :£ — Prof. R. Hartig has investigated the nature 
and the cause of the “ Roth-holz ” or “ bois rouge ” that is not uncommon 
in pine-wood. Red wood is produced especially when a tissue in process 
of formation is exposed to strong pressure in the direction of the longi- 
tudinal axis of the organ, this pressure being generally the result of a 
continuous wind. The tissue of the red wood is characterised, among 
other points, by the greater thickness of the walls of the tracheids ; 
and the chief purpose of the structure appears to be to increase the 
firmness of the stem. 
Secondary Growth in Thickness in Palms.§ — Herr H. Potonie 
confirms the conclusion arrived at by previous observers, that when any 
secondary increase in thickness takes place in the stem of palm-trees, it 
is always due to an increase in size of the cells of the fundamental 
parencliyme, and of the sclerenchymatous layer of the vascular bundles, 
never to any new formation. 
* Bot. Centralbl., lxvii. (1896) pp. 33-41, 65-73, 97-102, 129-33 (1 pi.). 
t SB. K. Akad. Wiss. Wien, civ. (1895) pp. 723-72. 
X Forstl.-naturw. Zeitschr., 1896, 3 ter Heft (6 figs.). See Bot. Ztg., liv. (1896) 
2 te Abth., p. 197. 
§ Naturwiss. Wochenschr., 1895, No. 4. See Bot. Centralbl., lxvii. (1896) p. 337. 
